Recovery of pure uranium compounds from ores



Sept. 28, 1954 l, HOFFMAN 2,6?9376 RECOVERY OF PURE URANIUM COMPOUNDSFROM ORES Filed June 17, 1942 PREFERRED P/PO CED U/EE GEN us OREPEEP/3R5 ORE Foe DIGEST/0N PULVER/LE J1 H N0 v 1"" [+1 3 V D/GE57' T l EW CONVERT URANIUM L 4- E P E To VA y UEAHYL NITRATE r- ETHER EXTRACTReam Q l 5U5JECT To EXTRACT f PERU/Y FOR I FURTHER URANYL NITRATE IETHE'? fXTEACT/D EXTRACT/0H WITH ETHER 0F Uzmuum NITRATE 47 .L

l H 0 Pue/E/Eo BYMIHOR l l s A 2 V WATER EXTRACTION 5 P20011615 5 i MTEEExTRAcTm/v Y RECOVER [JEAN/um FROM ETHEE EVAPOEA TE /GNITE 7b 5mmURANIUM 0x/ DE Jh/wEs Z HOFFMAN INVENTOR ATTORNEY Patented Sept. 28,1954 RECOVERY OF PURE URANIUM COMPOUNDS FROM ORES Application June 1'1,1942, Serial No. 447,465

(Granted under Title 35, U. S. Code (1952),

sec. 266) 4 Claims.

The invention or discovery described herein may be mad and used by orfor the Government of the United States without the payment to me of anyroyalty therefor.

This invention relates to a method of ore treatment, and moreparticularly to a method of recovering uranium oxide fromuranium-bearing ores as, for example, pitchblende, carnotite, autuniteor becquerelite.

Various methods have heretofore been proposed for the recovery ofuranium from such ores but in the main, such recovery has beenincidental to the disassociation of other elements, as for example,radium therefrom. Furthermore, the methods heretofore in use have beensubject to various disadvantages, such as the requirement of an unduelength of time, the recovery of uranium in an impure state, contaminatedby such substances as vanadium and/or molybdenum, and the necessity ofutilizing relatively expensive reagents.

The primary object of this invention is, therefore, the provision of aprocess of recovering uranium oxide directly from uranium-bearing oresin a high state of purity, in a comparatively rapid, simple andefficient manner by a method utilizing only relatively plentiful andinexpensive reagents.

A secondary object is the recovery of uranium as above stated in amanner calculated to reduce to a minimum the hazard of fire orexplosion.

Other objects will in part be obvious and in part, pointed outhereinafter, as the disclosure of the invention proceeds.

It may here be pointed out that present military as well as economicusages require increasing quantities of relatively pure uranium oxideand that, whereas heretofore uranium has been largely treated as aby-product, it has now become sound practice to recover uranium as aprincipal product, the various other constituents of the ores therebybecoming by-products. An additional advantage of the present invention,also, lies in the fact that after the extraction of uranium in themanner hereinafter described, the residual matter contains such elementsas radium in a materially increased concentration permitting arelatively high yield in radium recovery by known conventionalprocesses.

Referring now to the invention proper, it has heretofore been known thaturanyl nitrate UO2(NO3)2.6H2O is relatively highly soluble in ether butsuch facts have never, to my knowledge, been employed in uranium oretreatment. The present invention contemplates broadly the application ofnitric acid directly to uraniumbearing ores to convert the uraniumcontent to uranyl nitrate, the absorption of the uranyl nitrate inether, reabsorption of the uranyl nitrate from the ether in water,evaporation of the water and conversion of the uranyl nitrate to uraniumoxide, and is based on my discorvery that, unexpectedly, such processwhen carried out in the manner hereinafter described, effects arecovery, in a single treatment, of approximately two-thirds of theoriginal uranium content of the ore, substantially free from impuritieswhile leaving substantially all of the radium content in the residue,thus providing a relatively high residual concentration forsub-processing. It has further been discovered that retreatment, in themanner hereinafter described, of the residual matter resulting from theinitial extraction of two-thirds of the uranium content of the ore willfurther result in the extraction of substantially two-thirds of theremaining uranium. The process can, therefore, be carried out repeatedlyuntil the quantity of extracted uranium becomes so minute as to renderrepeated operations economically unsound.

In detail, on a laboratory scale, the invention may be practiced asfollows:

Example 1.-Ea3traction of uranium oxide from carnotite ore utilizingethyl ether Place 50.0 grams of pulverized carnotite (20 mesh or finer)in a 600 ml. beaker and add ml. of dilute nitric acid (1+1). Cover thebeaker and digest on a steam bath for approximately half an hour atabout 100 C. At the conclusion of this period uncover the beaker andevaporate the resultant solution to dryness. Allow the residue to cooland add approximately 15 ml. of water to loosen the mass in the beaker.The cooled residue may now be transferred to a 300 ml. Erlenmeyer flaskto facilitate handling. Add 50 ml. of ethyl ether [(C2H5) 20] to theflask, stopper and shake vigorously for two or three minutes. The ether,which should be almost clear, should now be poured off into a separatoryfunnel. Repeat this procedure three times (making four extractions inall) using 50 ml. of other each time.

Now to the combined extracts of ether add 2 ml. of water and shakevigorously for at least one minute, then allow the mixture to separateinto two layers and drain off the water. A relatively small portion ofthe uranyl nitrate may be retained in the water so drawn on and this maybe saved for subsequent treatment if it is desired to recover thisportion of the uranyl nitrate. Repeat the above operation twice, (makingthree extractions in all) each time utilizing two ml. portions of waterand withdrawing the water.

The ether in the separatory funnel now contains substantially all theuranyl nitrate in a relatively high state of purity.

It may here be pointed out that the various impurities found incarnotite and other uranium ores are, in the main, more soluble in waterthan in ether. Hence, the mixture and agitation of these two substanceswith as small a quantity of water as 1% will extract the bulk of theseimpurities from the ether. Uranyl nitrate, though more soluble in waterthan in ether, is nonetheless so soluble in ether as to be substantiallyunaffected by the relatively small percentage of water above described.A larger percentage of water will, however, as hereinafter described,result in the transfer of the relatively pure uranyl nitrate fromsolution in ether to solution in water.

After the steps above described, the ether may be cautiously evaporatedand the residue ignited at a temperature of 1000 C. in a known manner toproduce uranium oxide.

However, due to the possibility of violent reaction between ether anduranyl nitrate, if the temperature at which the ether is evaporatedbecomes too high, and likewise to conserve the ether for reuse, thefollowing procedure is preferred:

To the approximately 200 ml. of ether solution above described, add 20ml. (about of water and shake vigorously for one minute or more, allowthe liquid to separate into two layers and drain the water into asuitable receptable. Repeat with successive 20 ml. portions of wateruntil the ether above the water is substantially colorless. Three orfour such extractions are usually sufficient to extract the uranylnitrate, due to the relatively high solubility thereof in water, asmentioned previously. The remaining ether may be reutilized in treatingthe next batch of ore.

Now evaporation of the combined water extracts which may be accomplishedwithout undue risk of fire or explosion, will leave a residue ofsubstantially pure UO2(NO3)2.6H2O, which may be readily converted at1000 C. to U308 in a known manner.

Example 2.--Extraction of uranium oxide from uraninite or pitchblendeutilizing iso-propyl ether Place 50.0 grams of pulverized pitchblende(20 mesh or finer) in a suitable receptacle and add 100 ml. of dilutednitric acid (1+1) and proceed as in Example 1 to the step of addingether. Then add 250 ml. of iso-propyl ether (CHa l: cut

and agitate vigorously and drain off as in Example 1. Repeat thisprocess three times and. add to the combined ether so withdrawn ten ml.of water. Proceed as in Example 1 until substantially all the pureuranyl nitrate is in solution in the ether.

With iso-propyl as well as the ethyl ether it is desirable to redissolvethe uranyl nitrate in water and to accomplish this, 100 ml. of water maynow be added to the ether and the mixture agitated and separated asbefore, the process being repeated until the ether is substantiallycolorless, whereupon procedure as in Example 1 will yield uranium oxide.

The results achieved by the process described in Example 2 aresubstantially the same as those achieved in the process described inExample 1, with the exception that the use of ethyl ether results in theelimination of a slightly greater percentage of impurities and the yieldof slightly greater quantities of uranium due to the higher solubilityof uranyl nitrate therein.

In the accompanying drawing constituting a flow sheet, the reagentsemployed in the preferred procedure are indicated in the left handcolumn. The various process steps are indicated in the center column (itbeing noted that each step, although several repetitions thereof may berequired is indicated as a. single block), and the resultants are shownin the third column. Return of reagents for reuse is indicated by dottedlines. The fourth column to the right indicates the generic steps of theprocess.

As will be apparent from the foregoing descriptions and the attachedflow sheet, the process herein described is exceptionally rapid as wellas economical. The reagents emloyed, ether, nitric acid and water, areinexpensive and in the case of ether and nitric acid may be reutilizedrepeatedly, very small quantities being lost in successive operations.The recovery of uranium is thorough and, as previously pointed out, byretreatment of the residue, successive fractional portions of theremainder may be extracted until the yield becomes so minute as to beeconomically unwarranted. Furthermore, other constituents of the orewhich are regarded for the purpose of uranium extraction as impurities,but which may be of high value (1. e. radium) and rare earth elementsare left in condition to be readily recovered by known processes. Infact, in the case of radium the utilization of this process initiallyleaves in the ore a relatively higher radium concentration, thusfacilitating recovery thereof.

From the foregoing description it will now be apparent to those skilledin the art that the instant invention provides a practical, inexpensiveand relatively simple method of extracting uranium directly from ore ina manner fulfilling the stated objects of this invention and others,including many advantages of great commercial utility.

It is to be understood that all matter hereinbefore set forth is to beconsidered as illustrative and not in a limiting sense, and that thescope of the inventive concept is limited only by the appended claims.

I claim as my invention:

1. A method of obtaining highly purified U303 from a uranium containingore which comprises digesting the uranium containing ore with nitricacid to produce uranyl nitrate, evaporating said digested ore mass todryness, treating said dried ore mass with an aliphatic ether toselectively extract the uranyl nitrate therefrom, washing said etherextract with not more than 1% by volume of Water several times to removeimpurities, separating the purified ether layer successively from theseveral aqueous wash layers, extracting the highly purified uranylnitrate from the ether with several portions of Water, each having avolume of about 10% of the volume of the ether being extracted,combining said water extracts, evaporating said combined extract todryness to leave a residue of substantially pure UO2(NO3) 2.6H2O, andthe heating said residue at 1000 C. to convert it to U308- 2. A methodof obtaining highly purified U308 from a uranium containing ore whichcomprises digesting the uranium containing ore with nitric acid toproduce uranyl nitrate, evaporating said digested ore mass to dryness,treating said dried ore mass with an aliphatic ether to selectivelyextract the uranyl nitrate therefrom, washing said ether extract atleast twice with not more than 1% by volume of water to removeimpurities, separating the purified ether layer successively from theseveral aqueous wash layers, extracting the highly purified uranylnitrate from the ether at least twice with about by volume of water,combining said water extracts and evaporating them to dryness, andconverting the uranyl nitrate thus obtained to purified UaOa by heating.

3. A method of obtaining highly purified UaOa from carnotite whichcomprises digesting the carnotite with nitric acid to produce uranylnitrate, evaporating said digested ore mass to dryness, treating saiddried ore mass with ethyl ether to selectively extract the uranylnitrate therefrom, washing said ether extract at least twice with notmore than 1% by volume of water to remove impurities, separating thepurified ether layer successively from the several aqueous wash layers,extracting the highly purified uranyl nitrate from the ether at leasttwice with about 10% by volume of water, combining said water extractsand evaporating them to dryness, and converting the uranyl nitrate thusobtained to purified UaOa by heating.

4. A method of obtaining highly purified U308 from pitchblende whichcomprises digesting the pitchblende with nitric acid to produce uranylnitrate, evaporating said digested ore mass to dryness, treating saiddried ore mass with iso- References Cited in the file of this patentUNITED STATES PATENTS Number Name Date 440,143 Dode Nov. 11, 18901,897,740 Teller Feb. 14, 1933 2,211,119 Hixson Aug. 13, 1940 2,227,833Hixson Jan. 7, 1941 FOREIGN PATENTS Number Country Date 16,228 GreatBritain Sept. 14, 1916 OTHER REFERENCES Crookes, Proceedings of theRoyal Society of London, volume 66, pp. 409-422 (1900). (Copy inscientific Library.)

Boltwood, American Journal of Science, 4th Ser., volume 25, page 276(1908). (Copy in Scientific Library.)

Misciattelli, London, Edinburgh and Dublin Philosophical Magazine, 7thSer., volume 7, page 670 (1929). (Copy in Scientific Library.)

Treatise on Physical Chemistry, by Taylor, 2nd ed., vol I (1931), D. VanNostrand Co., Inc., New York, N. Y., pp. 485-487.

1. A METHOD OF OBTAINING HIGHLY PURIFIED U3O8 FROM A URANIUM CONTAININGORE WHICH COMPRISES DIGESTING THE URANIUM CONTAINING ORE WITH NITRICACID TO PRODUCE URANYL NITRATE, EVAPORATING SAID DIGESTED ORE MASS TODRYNESS, TREATING SAID DRIED ORE MASS WITH AN ALIPHATIC ETHER TOSELECTIVELY EXTRACT THE URANLY NITRATE THEREFROM, WASHING SAID ETHEREXTRACT WITH NOT MORE THAN 1% BY VOLUME OF WATER SEVERAL TIMES TO REMOVEIMPURITIES, SEPARATING THE PURIFIED ETHER LAYER SUCCES-